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(11) | EP 2 417 972 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
| published in accordance with Art. 153(4) EPC |
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| (54) | PHARMACEUTICAL COMPOSITION FOR TREATING OR PREVENTING BURN INJURIES |
| (57) The present invention relates to a pharmaceutical composition and the method of use
for treating or preventing burn injury in patients or subjects in need, including
the compound represented by the specific chemical formula as an active ingredient
or its pharmaceutically acceptable salts or solvates. |
TECHNICAL FIELD
[0001] The present invention relates to a pharmaceutical composition and the method of use for treating or preventing burn injury in patients or subjects in need.
BACKGROUND ART
[0002] Burns are mainly caused by accidents, and can be classified into thermal burns, burns caused by currents, chemical burns, and radiation burns according to the causes.
[0003] The severity of burns can be classified into first-degree, second-degree, third-degree, and fourth-degree burns according to the burned area, depth of burns, the temperature of and the contact time with the object causing burns, and skin condition. In second- or higher-degree burns, scars can be left and hospital cares are required.
[0004] First-degree burns make the skin red, and are accompanied by a tingling pain. Also, the outermost layer of the skin layer, the epidermis is damaged and often swollen, accompanied by pain and erythema.
[0005] The symptoms disappear within a few days, but light desquamation and pigmentation can be left in its place. After recovery, scars are not left. The case of sun burn is the most common example of first-degree burns.
[0006] Second-degree burns affect both the epidermis and dermis, and can cause redness, pain, swelling, and blisters within 24 hours after the accident. Also, this burn also affects the sweat gland and pores. Subjectively, severe burning-sensation or pain can be felt. If blisters burst, an eroded area of the skin is exposed and much of the liquid juice comes out. In case that burned area is over about 15% of body surface area, it needs special attention. Wound heals within a few weeks, but in many cases the pigmentation or depigmentation can be left in its place. If secondary infections occur, local symptoms become more severe and last long.
[0007] Third-degree burns affect the epidermis, dermis and hypodermis, make the skin black or translucent white and make blood clot beneath the surface of the skin. These burned areas may be numb, but patients may feel severe pain, and the necrosis of skin tissues and structures require a lot of time for the treatment, remaining scars later. In 2 weeks after the accident, the scab falls off, and ulcer sides appear. There are plenty of secreting fluids and it is easy to bleed, but gradually new tissue formation through epidermis regeneration heals the burn area, remaining scars. If skin necrosis is deep or secondary infection occurs, the healing process is delayed and scar surfaces become irregular, often leading to keloid generation and remaining of transformation, or movement disorders. If the burned area is about 10% of body surface area, it needs special attention.
[0008] Fourth-degree burns are cases that the burned tissue is carbonized and changed into black, and the layer of fat located under skin layer, ligaments, fascia, muscle or bone also suffers from burns. Fourth-degree burns occur by high-voltage electric injuries and sometimes, in case of fungal infection during deep second- and third-degree burns. If the range of burns is more than 20% of body surface area, body can cause physical reactions, hypotension due to excessive body fluid loss, shock, and acute renal failure may occur and later subsequent wound infection, pneumonia, sepsis, or multiple organ dysfunction syndromes may occur.
[0009] For the treatment of burns, it is important to heal the early burn wounds as fast as possible or to reduce the burned area. In the initial burn wound dressings, the initial treatment is emphasized to prevent the transition to deep burns by control of infection and inflammation, maintenance of humid environment, and treatment of growth factors or cytokines helping skin regeneration, local use of heparin etc.
[0010] If useful therapeutic compounds to treat or prevent burn injury are developed, it would be greatly helpful to treat patients with burns, improve the state, and reduce scars considering the severity of burn injury.
DISCLOSURE
Technical Problem
[0011] Accordingly, the object of the present invention is to provide a pharmaceutical composition and a medical method using the composition useful for treating or preventing burn injury.
Technical Solution
[0012] To solve the technical problem, the present invention provides a pharmaceutical composition for treating or preventing burn injury, comprising tetrafluorobenzyl derivatives represented by the below chemical formula 1 or its pharmaceutically acceptable salts or solvates as effective agents:
wherein,
R1, R2, and R3 are independently hydrogen or halogen;
R4 is hydroxy, alkyl, alkoxy, halogen, alkoxy which is substituted with halogen, alkanoyloxy or nitro;
R5 is carboxylic acid, ester of carboxylic acid with alkyl, carboxyamide, sulfonic acid, halogen, or nitro.
[0013] The present invention provides a pharmaceutical composition, or a medical method for treating or preventing burn injury, comprising tetrafluorobenzyl derivatives represented by the chemical formula 1 or its pharmaceutically acceptable salts or solvates.
[0014] Preferably, in the chemical formula 1, alkyl is C1-C5 alkyl, and more preferably C1-C3 alkyl. More specifically, preferable alkyl includes, but is not limited to, methyl, ethyl, propyl, isopropyl, butyl, sec-butyl and tert-butyl. Alkoxy, preferably, is C1-C5 alkoxy, and more preferably C1-C3 alkoxy. More specifically, preferable alkoxy includes, but is not limited to, methoxy, ethoxy, and propanoxy. Halogen includes, but is not limited to, fluoride, chloride, bromide, and iodide. Preferably, alkanoyl is C2-C10 alkanoyl, and more preferably C2-C5 alkanoyl. More specifically, preferable alkanoyl includes, but is not limited to, ethanoyl, propanoyl, and cyclohexanecarbonyl. Preferably, alkanoyloxy is C1-C4 alkanoyloxy.
[0015] Preferable examples of the tetrafluorobenzyl derivative represented by the above chemical formula 1 include, but are not limited to, followings:
2-Hydroxy-5-(2,3,5,6-tetrafluoro-4-trifluorcmethyl-tenzylamino)-benzoic acid (hereinafter, referred to as '2-Hydroxy-TTBA'),
2-Nitro-5-(2,3,5,6-tetrafluoro-4-trifluoromethylbenzylamino) benzoic acid,
2-Chloro-5- (2,3,5,6-tetrafluoro-4-trifluorcmethylbenzylamino) benzoic acid,
2-Brorno-5-(2,3,5,6-tetrafluoro-4-trifluoromethylbenzylanLino) benzoic acid,
2-Hydroxy-5-(2,3,5,6-tetrafluoro-4-methylbenzylamino)benzoic acid,
2-Methy1-5-(2,3,5,6-tetrafluro-4-trifluoromethylbenzylamino) benzoic acrid,
2-Methoxy-5- (2,3,5,6-tetrafluoro-4-trifluoromethylbenzylamino) benzoic acid,
5-(2,3,5,6-tetrafluoro-4-trifluoranethylbenzylamino)-2-trifluoromethoxy benzoic acid.
[0016] In the present invention, burns usually refer to the phenomenon that skin cells are destroyed by heat or lead to necrosis. Examples of burns include flame burns caused by fire, scalding burns caused by hot liquid (water, oil, etc.), contact burns caused by contact with hot objects (such as electric irons, rice cookers, etc.), chemical burns caused by strong acids, strong alkalis, sunburns caused by strong ultraviolet light, radiation burns caused by exposure to radiation and X-ray, but are not limited to. Also, the invention of burns can be first degree, second degree, third degree, and fourth degree burns.
[0017] The tetrafluorobenzyl derivative represented by the above chemical formula 1 or its pharmaceutically acceptable salts or solvates can be used for treating or preventing burn injury, but are not limited to specific type or degree (severity) of burns.
[0018] The tetrafluorobenzyl derivative or its pharmaceutically acceptable salts of the present invention can be prepared by, but is not limited to, the reaction schemes released in US 6,927,303.
[0019] Some compounds according to the present invention can be administered in the form of pharmaceutically acceptable salts. The term "pharmaceutically acceptable salts" of the present invention mean salts produced by non-toxic or little toxic base. In case that the compound of the present invention is acidic, base addition salts of the compound of the present invention can be made by reacting the free base of the compound with enough amount of desirable base and adequate inert solvent. Pharmaceutically acceptable base addition salts include, but are not limited to, lithium, sodium, potassium, calcium, ammonium, magnesium or salt made by organic amino. In case that the compound of the present invention is basic, acid addition salts of the compound of the compound can be made by reacting the free base of compound with enough amount of desirable acid and adequate inert solvent. Pharmaceutically acceptable acid addition salts include, but are not limited to, propionic acid, isobutylic acid, oxalic acid, malic acid, malonic acid, benzoic acid, succinic acid, suberic acid, fumaric acid, mandelic acid, phthalic acid, benzenesulfonic acid, p-tolylsulfonic acid, citric acid, tartaric acid, methanesulfonic acid, hydrochloric acid, bromic acid, nitric acid, carbonic acid, monohydrogencarbonic acid, phosphoric acid, monohydrogen-phosphoric acid, dihydrogen-phosphoric acid, sulfuric acid, monohydrogen.-sulfuric acid, hydrogen iodide, and phosphorous acid. In addition, the pharmaceutically acceptable salts of the present invention include, but are not limited to, a salt of amino acid like arginate and an analog of organic acid like glucuronic or galactunoric.
[0020] Some of the compounds of the present invention may be hydrated form, and may exist as solvated or unsolvated form. A part of compounds according to the present invention existing as a crystal form or amorphous form, and any physical form is included in the scope of the present invention. In addition, some compounds of the present invention may contain one or more asymmetric carbon atoms or double bonds, and therefore exist in two or more stereoisomeric forms like racemate, enantiomer, diastereomer, geometric isomer, etc. The present invention includes these individual stereoisomers of the compounds of the present invention.
[0021] The present invention also provides a pharmaceutical composition comprising the above compound or its pharmaceutically acceptable salts or solvates; and pharmaceutically acceptable excipients or additives, The tetrafluorobenzyl derivative represented by the above chemical formula 1 or its pharmaceutically acceptable salts/solvates of the present invention may be administered alone or with any convenient carrier, diluent, etc. and such a formulation for administration may be single-dose unit or multiple-dose unit.
[0022] The pharmaceutical composition of the present invention may be formulated in a solid or liquid form. The solid formulation includes, but is not limited to, a powder, a granule, a tablet, a capsule, a suppository, etc. Also, the solid formulation may further include, but is not limited to, a diluent, a flavoring agent, a binder, a preservative, a disintegrating agent, a lubricant, a filler, etc. The liquid formulation "includes, but is not limited to, a solution such as water solution and propylene glycol solution, a suspension, an emulsion, etc., and may be prepared by adding suitable additives such as a coloring agent, a flavoring agent, a stabilizer, a thickener, etc.
[0023] For example, a powder can be made by simply mixing the tetrafluorobenzyl derivative of the present invention, and pharmaceutically acceptable excipients like lactose, starch, microcrystalline cellulose etc. A granule can be prepared as follows: mixing tetrafluorobenzyl derivatives or its pharmaceutically acceptable salts, a pharmaceutically acceptable diluent and a pharmaceutically acceptable binder such as polyvinylpyrrolidone, hydroxyprdpylcellulose, etc; and wet-granulating with adequate solvent like water, ethanol, isopropanol, etc, or direct-compressing with compressing power. In addition, a tablet can be made by mixing the granule with a pharmaceutically acceptable lubricant such as magnesium stearate, and tabletting the mixture using a tablet making machine.
[0024] The pharmaceutical composition of the present invention may be administered in forms of, but not limited to, oral formulation, injectable formulation, (for example, intramuscular, intraperitoneal, intravenous, infusion, subcutaneous, inplant), inhalable, intranasal, vaginal, rectal, sublingual, transdermal, topical, etc. depending on the disorders to be treated and the patient's conditions. The composition of the present invention may be formulated in a suitable dosage unit comprising a pharmaceutically acceptable and non-toxic carrier, additive and/or vehicle, which all are generally used in the art, depending on the routes to be administered. A depot type of formulation being able to continuously release drug for desirable time also is included in the scope of the present invention.
[0025] The present invention also provides a method of using the tetrafluorobenzyl derivative or its pharmaceutically acceptable salts or solvates for treating and/or preventing burn injury; including the administration to objects that require treatment or prevention of burn injury with therapeutically effective amount.
[0026] For treating burn injury, the compound or its pharmaceutically acceptable salts or solvates of the present invention may be administered daily at a dose of approximately 0.01 mg/kg to approximately 1000 mg/kg, preferably approximately 2.5 mg/kg to approximately 500 mg/kg. However, the dosage may be varied according to the patient's conditions (age, sex, body weight, etc.), the severity of patients in need thereof, the used effective compounds, etc. The compounds of the present invention, may be administered once a day or several times a day in divided doses, if necessary.
Advantageous Effects
[0027] The present invention relates to a method and a pharmaceutical composition for treating burn injury, the compound represented by the chemical formula as an active ingredient or its pharmaceutically acceptable salts.
DESCRIPTION OF DRAWINGS
[0028]
Figure 1 shows the protective effect of 2-hydroxy-TTBA against a thermal burn injury using a result of blood chemistry test, that is, through reduction of lactate dehydrogenase in serum
Figure 2 is the photograph showing a result of morphological skin observation at 7 days after a thermal burn injury. This figure shows therapeutic effects of 2-hydroxy-TTBA for the burn injury.
Figure 3 is the photograph showing comparative states of epithelia stained by hematoxylin-eosin according to each experimental groups.
Figure 4 is the photograph showing the state of full-thickness skin in zone of stasis (zone of tissue injury) at 7 days after a thermal burn injury stained by hematoxylin-eosin under 10x microscope.
Figure 5 is the photograph showing the state of live cells of full-thickness skin tissues in zone of stasis (zone of tissue injury) stained by cresyl violet under 10x microscope.
Figure 6 is the photograph showing the state of collagen and muscle fibers of full-thickness skin tissues in zone of stasis (zone of tissue injury) through Masson's trichrom staining
MODE FOR INVENTION
[0029] Hereinafter, the present invention is described in considerable details to help those skilled in the art understand the present invention. However, various examples according to the present invention can be transformed into other forms, and the scope of the invention should not be construed as being limited to the following examples. Examples of the present invention are provided to explain more completely to the skilled artisan in this field.
<Example 1> The therapeutic effect against contact burn injury
[0030] To confirm the therapeutic effect of 2-hydroxy-TTBA. against burn injury, contact burn injury is induced for 30 seconds on the back of rats (on the both side of skin) using a brass comb preheated for 3 minutes in the boiling water (maintaining at 100 °C). After 5 minutes, 2-hydroxy-TTBA 10 mg/5 ml/kg were administered to intravenously for 5 minutes. Since then, twice-a-day administration (at an interval of 10-12 hours) was sustained for 7 days on the same conditions. The same amount of saline without the compound was administered to the vehicle-treated group in the same manner. Groups of burn experiments were same as below table 1.
[Table 1]
| Groups | Normal group | Burn (control group) | Vehicle-treated group | 2-hydroxy-TTBA-treated group |
| Total number of experimental animals | 6 | 9 | 8 | 7 |
| Number of dead animals | N/A | 2 | 0 | 0 |
| N/A : not applicable |
[0031] When analyzing the results, number of animals of the normal group for comparison, number of animals in each group, and the number of animals that died within 7 days after the burn injury were shown in above table 1. Two rats in the burn control group died at 5 and 7 days, respectively, after burn injury, but all of another experimental group survived.
The measurement of lactate dehydrogenase in serum through blood chemistry
[0032] Lactate dehydrogenase (LDH) is an enzyme distributed to almost all the tissues and catalyzing reversible reactions between pyruvic acid and lactic acid.
[0033] It is know that serum LDH level is elevated when tissues and cells are destroyed. Thus, the amount of LDH was measured in serum samples from each group except hemolyzed samples that may interfere with test results. The result was shown in the figure 1.
[0034] As shown in the figure 1, the LDE value of the burn control group was increased approximately 2 times compared to the normal group and the LDH value of 2-hydroxy-TTBA-treated group was reduced significantly compared to burn control group.
Observation of skin appearance on the back after bu= injury
[0035] Figure 2 is photographs that observed skin on the back 7 days after burn injury. Full thickness burns were induced in the both sides of back of experimental rats using a preheated brass comb with 4 rectangular shapes of size 10 x 20 mm. At 2 hours after induction, 4 pale-colored or darkish zones of coagulation (or zones of tissue necrosis) and 3 zones of stasis. (or zones of tissue injury) appeared on the both sides of back. The zone of coagulation (or zone of tissue necrosis) is a cell region that damaged irreversibly, and the recovery is impossible over time, and the zone of stasis (or zone of tissue injury) is a region that cell necrosis is continued without a specific treatment within 24 ~ 48 hours, leading to cell death by ischemia caused by continuous fibrin deposition, vasoconstriction, thrombosis, etc.
[0036] Therefore, to evaluate the efficacy in this experiment, among the zone of stasis, the remaining 4 regions (a rectangular area indicated the dotted lines) except regions toward the head close to a medication vest among 6 areas appeared in a single rat were analyzed.
[0037] As shown in the figure 2, formation of crust in the zone of stasis, switch to the wound, separation of wounds, or elimination of skin may be observed in the burn control group without taking any action.
[0038] Formation of eschar such as scab occurred rarely in the vehicle and 2-hydroxy-TTBA-treated group. Specially, the skin of 2-hydroxy-TTBA-treated group was restored to such a good skin condition that hair growth can be observed by the naked eye.
Histological appearance of eschar formation and_ wound epidermis formation after burn injury
[0039] Figure 3 is the result comparing the state of the epithelial layer through hematoxylin-eosin staining of tissues according to the groups. As shown in figure 3, unlike normal controls that normal epithelial layers (part indicated by the arrow) as well as healthy follicles were observed, normal epithelial cells except the inflammatory cells were not observed due to eschar formation in the burn control group. It was identified that wound epidermis formation was in progress in the vehicle-treated and 2-bydroxy-TTBA-treated groups. Some cases that hyperplasia of epidermis thicker than normal epithelial layers occurred could be also observed.
[0040] Eschar formation and frequency of wound epidermis formation was measured by analyzing total 28 tissue areas per group (4 zones of stasis per rat, 7 rats per group). As a result, the wound switching frequency of approximately 93% occurred in the burn control group was decreased to about 18% and 4%, respectively, in the veheicle-treated and 2-hydroxy-TTBA-treated groups. Also, the rate of wound epidermis formation was increased by approximately 32% and 72%, respectively, in comparison with the burn control group. The result was shown in the below table 2 (histological appearance: Eschar Formation and frequency of wound epidermis formation).
[Table 2]
| Groups | Burn control group | Vehicle-treated group | 2-hydroxy-TTBA-treated group |
| Eschar formation (%) | 92.857 | 17.857 | 3.571 |
| Wound epidermis formation (%) | 10.714 | 32.143 | 71.429 |
Histology of full-thickness skin by hematoxylin-eosin staining
[0041] Figure .4 was the photograph that observed the state of tissues of full-thickness skin through hematoxylin-eosin staining via 10x microscope.
[0042] It showed that epithelium, dermis, subcutaneous tissue and muscle layers have been damaged across the full thickness in the burn control group. It was observed that eschar .was formed, the inflammatory cells were infiltrated below it, and there are a large number of inflammatory cells between the subcutaneous tissue and muscle layers. In the vehicle-treated group, schar such as scab was not formed, but a considerable amounts of inflammatory cells were observed all over the skin tissues and subcutaneous tissues, still showing infiltration of the many inflammatory cells below the regenerated epithelium. In 2-hydroxy-TTBA-treated group, infiltration of inflammatory cells was considerably inhibited except in the areas of muscle cells and subcutaneous tissues and not only a wound epidermis formation but also protective effects even in the hair follicles, sebaceous glands and muscle layers appeared.
Histology of skin full-thickness by cresyl violet staining
[0043] Figure 5 is the photograph observed the live cells in the zone of stasis by cresyl violet staining via 10x microscope. In the burn control group and the vehicle-treated group, follicles were rarely observed and large amounts of inflammatory cells were observed throughout the full-thickness skin. On the other hand, live follicles and epithelia were observed, and relatively few inflammatory cells were observed in 2-hydroxy-TTBA-treated group.
Histology of full-thickness skin by Masson's trichrom staning
[0044] Figure 6 is the photograph that observed collagen of skin tissues and muscle fibers in the zone of stasis by Masson's trichrom staining. In the normal group, blue-stained collagen was evenly distributed throughout the dermis, and muscle fibers were stained red. In the burn control group, collagen was deposited irregularly below eschar, the level of staining was weak relative to the normal group. Almost of the muscle fibers were damaged and were not stained. In the vehicle-treated group, the amount of collagen was most abundantly observed relative to the other groups, even to a very high level compared to the normal control. In addition, the muscle fibers with damage were not stained, and significant amount of bleeding and infiltration of inflammatory cells were accompanied. However, in 2-hydroxy-TTBA-treated group, similar to the normal group, epithelium, dermis, subcutaneous fat, and muscles layers were well arranged, showing evenly distributed collages around the live hair follicles, and red-stained muscle fibers.
1. A pharmaceutical composition for treating or preventing burn injury, comprising tetrafluorobenzyl
derivatives represented by the chemical formula 1 or its pharmaceutically acceptable
salts as effective agents:
wherein,
R1, R2, and R3 are independently hydrogen or halogen;
R4 is hydroxy, alkyl, alkoxy, halogen, alkoxy which is substituted with halogen, alkanoyloxy or nitro;
R5 is carboxylic acid, ester of carboxylic acid with C1-C4 alkyl, carboxyamide, sulfonic acid, halogen, or nitro.
wherein,
R1, R2, and R3 are independently hydrogen or halogen;
R4 is hydroxy, alkyl, alkoxy, halogen, alkoxy which is substituted with halogen, alkanoyloxy or nitro;
R5 is carboxylic acid, ester of carboxylic acid with C1-C4 alkyl, carboxyamide, sulfonic acid, halogen, or nitro.
2. The pharmaceutical composition of claim 1, wherein the tetrafluorobenzyl derivative
is any one selected from the group consisting of
2-hydroxy-5- (2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-benzoic acid,
2-nitro-5- (2,3,5,6-tetrafluoro-4-trifluorcimethyl-benzylamino) - benzoic acid,
2-chloro-5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-benzoic acid,
2-bromo-5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-benzoin acid,
2-hydroxy-5-(2,3,5,6-tetrafluoro-4-methyl-benzylamino)-benzoic acid,
2-methyl-5- (2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino) - benzoic acid,
2-methoxy-5-(2,3,5,6-tetrafluoro-4-trifluoramethyl-benzylamino)-benzoic acid,
5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-2-trifluoromethoxy benzoic acid.
2-hydroxy-5- (2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-benzoic acid,
2-nitro-5- (2,3,5,6-tetrafluoro-4-trifluorcimethyl-benzylamino) - benzoic acid,
2-chloro-5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-benzoic acid,
2-bromo-5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-benzoin acid,
2-hydroxy-5-(2,3,5,6-tetrafluoro-4-methyl-benzylamino)-benzoic acid,
2-methyl-5- (2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino) - benzoic acid,
2-methoxy-5-(2,3,5,6-tetrafluoro-4-trifluoramethyl-benzylamino)-benzoic acid,
5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-2-trifluoromethoxy benzoic acid.
3. The pharmaceutical composition of claim 2, wherein the tetrafluorobenzyl derivative
is 2-hydroxy-5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino) benzoic acid.
4. A method of use for treating or preventing burn injury, comprising administering to
a subject in need thereof a therapeutically effective amount of the tetrafluorobenzyl
derivatives represented by the chemical formula 1 or its pharmaceutically acceptable
salts:
wherein,
R1, R2, and R3 are independently hydrogen or halogen;
R4 is hydroxy, alkyl, alkoxy, halogen, alkoxy which is substituted with halogen, alkanoyloxy or nitro;
R5 is carboxylic acid, ester of carboxylic acid with C1-C4 alkyl, carboxyamide, sulfonic acid, halogen, or nitro.
wherein,
R1, R2, and R3 are independently hydrogen or halogen;
R4 is hydroxy, alkyl, alkoxy, halogen, alkoxy which is substituted with halogen, alkanoyloxy or nitro;
R5 is carboxylic acid, ester of carboxylic acid with C1-C4 alkyl, carboxyamide, sulfonic acid, halogen, or nitro.
5. The method of claim 4, wherein the tetrafluorobenzyl derivative is any one selected
from the group consisting of
2-hydroxy-5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-benzoic acid,
2-nitro-5-(2,3,5,6-tetrafluoro-4-trifluoramethyl-benzylamino)-benzoic acid,
2-chloro-5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-benzoic acid,
2-bromo-5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-benzoic acid,
2-hydroxy-5-(2,3,5,6-tetrafluoro-4-methyl-bexzylamino)-benzoic acid,
2 -methyl-5- (2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino) - benzoic acid,
2-methoxy-5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-benzoic acid,
5-(2,3,5,6-tetrafluoro-4-trifluoramethyl-benzylamino)-2-trifluoromethoxy benzoic acid,
2-hydroxy-5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-benzoic acid,
2-nitro-5-(2,3,5,6-tetrafluoro-4-trifluoramethyl-benzylamino)-benzoic acid,
2-chloro-5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-benzoic acid,
2-bromo-5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-benzoic acid,
2-hydroxy-5-(2,3,5,6-tetrafluoro-4-methyl-bexzylamino)-benzoic acid,
2 -methyl-5- (2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino) - benzoic acid,
2-methoxy-5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-benzoic acid,
5-(2,3,5,6-tetrafluoro-4-trifluoramethyl-benzylamino)-2-trifluoromethoxy benzoic acid,
6. The method of claim 5, wherein the tetrafluorobenzyl derivative is 2-hydraxy-5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)
benzoic acid.
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.
Patent documents cited in the description